The invention relates to a method of generating steam in a forced-through-flow boiler or steam generator, in particular a BENSON boiler where during operation of the boiler, water is conveyed at least through a preheater, an evaporator and, if needed, a superheater, and during the start-up phase, and if desired in low load states, a water-steam mixture is conveyed to a separation tank, from which steam is withdrawn and separated feed water is supplied to the preheater.
With forced-through-flow boilers that are direct fired with fossil fuels, the evaporator, in which the water path is disposed downstream of the feed water preheater, contains a relatively small quantity of water which at the beginning of the formation of steam can be easily withdrawn via the separation tank.
Where waste heat steam generators, especially those disposed after gas turbines, are embodied as forced-through-flow boilers, care must be taken that due to the relatively great quantities of flue gas, evaporator heat transfer surfaces having a large water content are provided. Thus, during start-up of such steam generators, one must count on a large water discharge.
It is therefore an object of the present invention to provide a method of the aforementioned general type that is suitable in a straightforward manner to generate steam in a forced-through-flow steam generator that operates with waste heat.